November 16, 2012

Equator Ran Through Western North America 450 Million Years Ago

According to an international team of scientists, led by the University of Durham, UK, the recent storms that have battered the east coast of America may have been much more frequent in the region 450 million years ago.

The findings of their study, published in the journal Geology, pinpoint the positions of the Equator and the landmasses of the USA, Canada and Greenland, during the Ordovician Period 450 million years ago, indicating the equator ran down the western side of North America with a hurricane belt to the east.

This hurricane belt affected an area that covers modern day New York State, New Jersey and most of the eastern seaboard. The team used the distribution of fossils and sediments to map the line of the Ordovician Equator down to southern California.

This new research is the first to accurately locate and map the ancient Equator and adjacent tropical zones, while previous studies had fueled controversy about the precise location of the ancient equator. The team says these new results reveal how fossils and sediments can accurately track equatorial change and continental shifts over time.

Professor David Harper, Department of Earth Sciences, Durham University, UK, in a statement, said: "The equator, equatorial zones and hurricane belts were in quite different places in the Ordovician. It is likely that the weather forecast would have featured frequent hurricane-force storms in New York and other eastern states, and warmer, more tropical weather from Seattle to California."

The scientists believe there would have been similar climate belts to those of today since polar regions existed 450 million years ago.

The team, which included scientists from Canada, Denmark and the USA, discovered a belt of undisturbed fossils and sediments more than 3,700 miles long. The belt, which lacks typical storm-related sedimentary features where the deposits are disturbed by bad weather, stretched from the southwestern United States to North Greenland. Like the equatorial zone today, the Late Ordovician equatorial zone had few hurricane-grade storms.

Sedimentary deposits recorded on either side of the belt provide evidence of disturbance by severe storms, however. Generally, hurricanes form in the areas immediately outside of equatorial zones where temperatures of at least 80 degrees Fahrenheit combine with the Earth's rotation to create storms. The team believes the hurricane belts would have existed in the tropics on either side of the ancient equator.

Undisturbed fossil accumulations and sediments defined the position of the equatorial belt, which is coincident with the Late Ordovician equator as interpreted from magnetic records that were taken from rocks of a similar age from the region. This provided the team with a precise equatorial location and confirmed the Earth's magnetic field operated much in the same way as it does today.

Using the evidence of the disturbed and undisturbed sedimentary belts together with burrows and shells, the team pieced together the giant jigsaw map, enabling them to see that North America sat on either side of the Equator.

Christian Rasmussen, University of Copenhagen, said, "The layers of the earth build up over time and are commonly exposed by plate tectonics. We are able to use these ancient rocks and their fossils as evidence of the past to create an accurate map of the Ordovician globe."

Professor Harper added, "The findings show that we had the same climate belts of today and we can see where North America was located 450 million years ago, essentially on the Equator."

"While the Equator has remained in approximately the same place over time, the landmasses have shifted dramatically over time through tectonic movements. The undisturbed fossil belt helps to locate the exact position of the ancient Laurentian landmass, now known as North America."